What does it say about a country when its sanest citizens appear to be the secret police? In Dror Moreh’s stunning documentary “The Gatekeepers,” a half-dozen grizzled old men talk openly about their experiences running Shin Bet, Israel’s internal security service and primary anti-terrorism unit. (Very roughly, the organization is to Mossad what our FBI is to the CIA.) They’re a varied bunch, some cagey, others bureaucratic, more than one strikingly forthright.

And while they confess — sometimes grudgingly — to misdeeds and miscalculations, to blood on their hands both guilty and innocent, they mourn Israel’s gradual turn away from a two-state solution and toward brute force and oppression. These are aging warriors of realpolitik who’ve grown weary of carrying secrets. Says one, upending the old cliché about age turning liberals into conservatives, “When you retire [from Shin Bet], you become a bit of a leftist.”

“The Gatekeepers,” which was nominated for a 2012 feature documentary Oscar (“Searching for Sugar Man,” a much more feel-good exercise, won), plays a little like “Zero Dark Thirty” as directed by Errol Morris. It’s about spycraft, but it goes to the source. If for no other reason, it deserves to be seen for arranging decades of events in the Middle East into a chronology that, to an outsider, makes dreadful sense.

Taking as his starting point the 1967 Six-Day War that saw Israel decisively fighting back against neighboring Arab states and pushing into the West Bank, East Jerusalem, and the Gaza Strip, director Moreh has his subjects take us through years of brief hopes and lasting debacles: the coming of terrorism and the PLO, the 1982 Lebanon War, the first Intifada (there’s astonishing footage from the streets here), the 1993 Oslo Accords brokered by President Clinton, the ensuing rise of a violent Jewish religious right that tried to bomb the Dome of the Rock and that ultimately led to the 1995 assassination of Prime Minister Yitzhak Rabin. And on and on.

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Shin Bet’s place in all of this is complex and hardly flattering. Moreh repeatedly presses his subjects on some of the more notorious examples of the agency’s zeal: the beating and execution of two unarmed hijackers in the 1984 “Bus 300 Affair”; the 2002 assassination of Hamas leader Salah Shehadeh by dropping a 1-ton bomb on a crowded Gaza City neighborhood (14 others were killed, including eight children). Discussing the former incident, Avraham Shalom (Shin Bet director from 1981 to 1986) stops looking like a cuddly uncle and reveals the cold rationalist within. “You killed a terrorist whose hands were tied,” the director asks him — how is that moral? The response: “With terrorists, there are no morals.”

The Gatekeepers

★★★★

MPAA rating:

PG-13

MPAA rating reasons:

violent content, disturbing images

Language:

In Hebrew, with subtitles

Running time:

95 minutes

Cast:

Avraham Shalom, Carmi Gillon, Ami Ayalon

Director:

Dror Moreh

Playing at:

Coolidge Corner, Kendall Square, West Newton

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Other former leaders of the agency are more thoughtful, openly admitting how their work eroded their souls, both as Jews and as human beings. They all reserve a special contempt for the politicians who, we’re told, demand binary solutions to situations of endless gray and who “abandon the wounded in the field” at the first sign of bad press. They rage and agonize over the violent Israeli right, led by extremist rabbis. Carmi Gillon (director from 1994 to 1996) almost weeps as he talks of seeing Rabin’s assassination coming and feeling powerless to save his old friend.

And all of them point to moments where Israel could have more vigorously pursued a peaceful solution, a Palestinian state; all of them feel that the current situation in Gaza and the West Bank “is a brutal occupation force, similar to the Germans in WWII” (Shalom), that “we are making the lives of millions unbearable” (Gillon). Some of this is surely 20-20 hindsight. But much of it feels like clarity, coming as it does from men paid to have the country’s clearest vision. The Shin Bet directors were good at what they did — killing people, uncovering plots, capturing Israel’s enemies without and within — but their pride struggles with a greater sense of futility, even a regret that almost (but not quite) backs into guilt.

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